1. Field of the Invention
The present invention relates to a display device provided with a self-emission element, especially to a display device provided with an electroluminescenct element and a thin film transistor.
2. Description of the Related Art
In recent years, an electroluminescenct (hereafter, referred to as an EL) display device with an EL element has been receiving an attention as a display device substituting for a CRT and an LCD. For example, research and developments are being pursued for the EL display device provided with a thin film transistor (hereafter, referred to as a TFT) as a switching device for driving the EL element.
The above EL display device is formed, for example, by laminating the TFT and an organic EL element sequentially on a transparent glass substrate (hereafter, referred to as an insulating substrate).
A gate electrode is formed on the insulating substrate, and a gate insulating film and an active layer made of a p-Si film are laminated sequentially thereon.
In the active layer, a channel is provided above the gate electrode and source and drain regions are severally provided on both sides of the channel above the gate electrode.
An interlayer insulating film is formed on whole surfaces of the gate insulating film and the active layer, and a drain electrode is formed by filling metal such as Al in a contact hole provided correspondingly to the drain region.
Furthermore, on a whole surface of the interlayer insulating film, there are formed a flattening insulation layer for flattening the surface, which is made of, for example, an organic resin, and a contact hole on a position corresponding to the source region in the flattening insulation layer. On the flattening insulation layer, there is formed an anode of the EL element, which serves as a source electrode made of ITO (Indium Tin Oxide) and contacting to the source region through the contact hole.
A hole transport layer is formed on the anode of ITO and an emission layer is formed thereon. An electron transport layer is formed to cover the emission layer and a cathode is laminated thereon.
Here, there will be described a sealing configuration of a conventional EL display device, referring to the above substrate integrated with the EL element as a device substrate.
First, the device substrate and a sealing substrate made of a glass substrate are attached together with a sealing resin which is made of, for example, an epoxy resin and coated on the sealing substrate by a dispenser. The device substrate and the sealing substrate are attached together by heating and hardening the sealing resin interposed therebetween.
In heating and pressing processes for the adhesion of the device substrate and the sealing substrate, inert gas filling the EL display device expands. At that time, an opening as an escape route for the expanding inert gas must be provided in the sealing resin in order to avoid bursting of the sealing resin. Therefore, this opening is closed after filling the inert gas.
When the opening is closed after the adhesion as described above, however, moisture etc can be mixed in the EL display device to cause deterioration of the EL display device.
Adhesion of the substrates without forming the opening can provide a risk of bursting the sealing resin by a pressure differential between an inside and an outside of the EL display device.
The invention provides a display device manufacturing method including providing a device substrate having a display element thereon, providing a sealing substrate, and forming a layer of a sealing resin on the sealing substrate. The viscosity of the sealing resin is equal to or higher than 40000 cp when the layer of the sealing resin is formed. The method also includes placing the sealing substrate on the device substrate so that the layer of the sealing resin is disposed between the sealing substrate and the device substrate, and heating the layer of the sealing resin to harden the sealing resin so that the sealing substrate and the device substrate are attached together by the sealing resin. The layer of the sealing resin surrounds the display element after the attaching of the sealing substrate and the device substrate.
The invention provides another display device manufacturing method including providing a device substrate having a display element thereon, providing a sealing substrate, and forming a layer of a sealing resin on the device substrate so that the layer of the sealing resin surrounds the display element. The viscosity of the sealing resin is equal to or higher than 40000 cp when the layer of the sealing resin is formed. The method also includes placing the sealing substrate on the device substrate so that the layer of the sealing resin is disposed between the sealing substrate and the device substrate, and heating the layer of the sealing resin to harden the sealing resin so that the sealing substrate and the device substrate are attached together by the sealing resin.